Interface devices between an operator and a machine are used to input command signals and other information to control the machine. One type of interface device is configured to be manipulated by an operator and controls the machine by generating and sending a signal based on the position of the device. One example of such a device is a joystick. Many joysticks are spring-loaded so that the joystick is biased toward a central, neutral position. Accordingly, when the joystick is released at a location other than the neutral position, the biasing force restores the joystick to the central, neutral position.
Often, interface devices, as well as the machines they operate, are subject to electronic noise or feedback signals that may distort a true input signal. Electronic noise or feedback may be caused by a variety of factors, including flux fields and magnetic fields generated within proximity of the interface device or communication wires between the interface device and the controller. Further, some small, inadvertent movements of the interface device may distort a desired input signal. Because of this electronic noise, feedback, possible inadvertent movement, the control signal may vary from moment to moment, even when the interface device itself is not moving or when interface device movement is undesirable. Thus, in some instances, even though there may be no signal being generated at the interface device, a controller may still receive a signal generated as electronic noise.
One method of filtering the electronic noise, feedback, and small inadvertent signals includes generating a deadband around the neutral position of the interface device, such as the neutral position of a spring-loaded joystick. The deadband is a filtering zone that filters a signal, for example, a signal which varies from an average signal by less than half the width of the deadband. The filtered signal is not treated as an input by the controller. In contrast, when the signal is outside the width of the deadband, the controller considers the signal.
One known system that uses a deadband is disclosed in U.S. Pat. No. 6,750,845 to Hopper. The '845 patent discloses a computer pointing device that may be used to control a cursor on a machine, such as a computer. The pointing device is configured so that it may be operated in environments that may be perpendicular or non-perpendicular to a gravitational field and includes a deadband about its neutral region. When the pointing device is subject to non-perpendicular gravitational forces, the input device may be at rest outside its deadband. When this occurs, a user can activate and instruct the computer to create a new deadband around the resting position. However, the computer pointing device in the '845 patent requires that an operator affirmatively select the new deadband position. Further, the pointing device in the '845 patent is not configured to be used with a non-biased joystick.
This disclosure is intended to address one or more of the deficiencies of the prior art.